Photoredox catalysis has attracted wide attention in the last decade due to its great expansion of synthetic organic toolbox.[1] Typically, the key electron transfer (ET) step in photoredox catalysis follows light-induced non-adiabatic outer-sphere ET mode, which requires formation of a loose encounter complex between the excited photocatalyst and the substrate.[2] In this process, a suitable overpotential, according to Marcus theory, is generally desirable to achieve efficient ET kinetics.[3] Inner-sphere ET,[4] on the other hand, can be achieved adiabatically between close bind species (for example, electron donor-acceptor (EDA) complex[5]). Within these species, the crossing of high potential energy surface is circumvented via strong electronic coupling, resulting in significantly faster ET than that predicted by the outer-sphere mode.[6] In this presentation,[7] we will discuss a new example in which the inner-sphere ET between substrate and photocatalyst plays a critical role to overcome the unfavorable ET energetics. Due to the “π-hole–π” interaction between polyfluoroarenes (FA) and pyrene-based photocatalysts (Py), photo-induced ET proceeds smoothly against a large underpotential (delta GET up to 0.63 eV) and initiates the subsequent hydrodefluorination (HDF). The steric hindrance of Py and FA largely dictates the HDF reaction rate, pointing to an inner-sphere electron transfer pathway. [1] a) Prier, C. K.; Rankic, D. A.; MacMillan, D. W. Chem. Rev., 2013, 113, 5322; b) Skubi, K. L.; Blum, T. R.; Yoon, T. P. Chem. Rev., 2016, 116, 10035; c) Romero, N. A; Nicewicz, D. A Chem. Rev., 2016, 116, 10075 [2] a) Narayanam, J. M.; Stephenson, C. R. Chem. Soc. Rev. 2011, 40, 102; b) Pitre, S. P.; McTiernan, C. D.; Scaiano, J. C. Acc. Chem. Res. 2016, 49, 1320 [3] Marcus, R. A. Angew. Chem. Int. Ed. 1993, 32, 1111 [4] Taube, H. Angew. Chem. Int. Ed. 1984, 23, 329 [5] a) Rosokha, S. V.; Kochi, J. K. Acc. Chem. Res. 2008, 41, 641; b) Arceo, E.; Jurberg, I. D.; Alvarez-Fernandez, A.; Melchiorre, P. Nat. Chem. 2013, 5, 750; c) Lima, C. G. S.; de M. Lima, T.; Duarte, M.; Jurberg, I. D.; Paixão, M. W. ACS Catal. 2016, 1389; [6] a) Asahi, T.; Mataga, N. J. Phys. Chem. 1989, 93, 6575; b) Asahi, T.; Mataga, N. J. Phys. Chem. 1991, 95, 1956. [7] Lu, J.; Khetrapal, N. S.; Johnson, J. A.; Zeng, X. C.; Zhang, J. J. Am. Chem. Soc. Manuscript under revision

π-Hole–π interaction promoted photocatalytic hydrodefluorination via inner-sphere electron transfer

253rd National Meeting (2017)

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